1. Field of the Invention
This invention relates broadly to endoscopic instruments. More particularly, this invention relates to electrodes which are used in electrocautery probes with a resectoscope.
2. State of the Art
Electrosurgical resection is a procedure in which damaged or enlarged tissue is excised with an electrocautery probe. Transurethral resection is an electrosurgical procedure in which a portion of the prostrate is excised by means of an instrument passed through the urethra. Endometrial ablation is an electrosurgical alternative procedure to hysterectomy for women with menorrhagia (abnormal or excessive uterine bleeding). In both procedures, the instrument typically used is called a resectoscope or hysteroscope. Prior art FIG. 1 shows a typical resectoscope 10 with an electrocautery probe 12. The resectoscope 10 includes a distal guide tube 14 and a proximal handle 16. A telescope 18 is inserted through the guide tube 14 and is provided with a proximal eye piece 20 for viewing the interior of the bladder or other operative site. The cautery probe 12 has a distal electrode 22 which is mounted between a pair of arms 23, 25. The arms 23, 25 are joined at their proximal ends to an electrode lead 27 which is coupled via the handle 16 to a wire 24 which is coupled to a source of cautery current (not shown). A mounting sleeve 29 is provided on the probe 12 for slideably coupling it to the guide tube 14. The mounting sleeve 29 is typically located at the point where the arms 23, 25 are joined to the electrode lead 27. The handle 16 is generally capable of axially sliding the probe 12 and its distally mounted electrode 22 relative to the guide tube 14.
The resection procedure involves applying a cauterizing voltage to the electrode 22 and moving the electrode slowly through or over the prostate or endometrium while viewing the tissue through the scope 18. Thermal energy (in the form of an electrical signal) is applied through the electrode to the prostate or the endometrium so that tissue is excised. The resectoscope and cautery probe are also useful in other procedures for resecting the uterus, ureter, or renal pelvis.
Known electrodes for use in resectoscopes are available in many different shapes and sizes. U.S. Pat. No. 4,917,082 to Grossi et al., for example, discloses several embodiments of a "Resectoscope Electrode" including a coagulating electrode, a knife electrode, a punctate electrode, and a roller electrode, among others. Electrodes for use with resectoscopes are also widely available from Olsen Electrosurgical, Inc., Concord, Calif. They are available as blades, needles, balls, loops, spear tips, flexible wires, semi-circular wires, hooks, spatulas and blunt tips.
Most of the known electrodes extend downward from a pair of probe arms and present a single working surface which is located below the axis of the probe arms and below the axis of the scope. Thus, in order to operate on tissue which is located above the probe arms, the entire resectoscope must be rotated 180.degree. to bring the working surface of the electrode in contact with the tissue. U.S. Pat. No. 5,007,907 to Nishigaki et al. and U.S. Pat. No. 5,196,011 to Korth et al. disclose electrodes which are suspended from a single probe arm. Nishigaki et al. discloses a special probe arm which is located above the scope and which has a loop which extends below the axis of the probe arm. Korth et al. discloses an electrode in the shape of a triangle which is suspended at its vertex from a single probe arm. While these patents would appear to show "full loop" electrodes, the electrodes shown do not have upper and lower working surfaces.